Produktverteilung und Mechanismus der Gesamtreaktion der Formose-Reaktion / Product Analysis and Mechanism of the Formose Reaction

Abstract

<jats:title>Abstract</jats:title><jats:p> By means of liquid chromatographic analysis, UV, <jats:sup>13</jats:sup>C NMR and GC-MS spectroscopy it is possible to determine quantitatively the most important intermediate and final products of the formose reaction. As stable main products xylose, glucose and dendroketose, as stable side products ribose, lyxose, arabinose, mannose, dendroaldose, fructose and sorbose are identified. Instable intermediates are glycolaldehyde, glycerolaldehyde, dihydroxiacetone, erythrose, threose and pentuloses. Cannizzaro reaction, oligomerization and the primary formose reaction are catalyzed by a calcium hydroxide bismethylene glycolate complex.</jats:p>

Deuterium Studies Reveal a New Mechanism for the Formose Reaction Involving Hydride Shifts

“…Normally aldehydes are more rapidly enolized than their ketone isomers, but in water the carbonyl group of aldehyde 2 is extensively hydrated; the proton NMR spectrum of 2 in D 2 O shows less than 1% of the aldehyde, with the rest a geminal diol. The keto group of 3 is 80% a ketone and 20% a geminal diol in D 2 O (as observed by 13 C NMR spectroscopy). Thus, the fastest route to the enediol 1,2,3-trihydroxypropene is not by enolization of 2 but instead by its more rapid conversion to 3 by hydride shift followed by the rapid enolization of 3.…”

Putative mechanism of the sugar formation on prebiotic Earth initiated by UV-radiation

“…Hence, all earlier versions that the formose reaction can be initiated by glycolaldehyde formed from two molecules of formaldehyde are invalid (see, e.g. Harsch et al, 1983). Seemingly, the observed formaldehyde condensation into monosaccharides in the absence of initiators, as has been reported in many earlier works, occurs due to a low quality of formaldehyde used by the researchers for their experiments.…”

“…1, 1) the formaldehyde dimerization under conditions identical to the conditions of the formose reaction (e.g. Harsch et al, 1983). However, such dimerization has been shown to be impossible, since only disproportionation of formaldehyde into methanol and formic acid by the Cannizzaro reaction takes place in the aqueous formaldehyde solutions in the absence of the monosaccharide primer (Socha et al, 1981):…”

Prebiotic sugar synthesis: Hexose and hydroxy acid synthesis from glyceraldehyde catalyzed by iron(III) hydroxide oxide

“…The catalytic activity of these inorganic substances together with that of iron oxide suggests that there may be other minerals that catalyze this important prebiotic condensation reaction. Catalysis of prebiotic sugar synthesis by minerals seems much more plausible than catalysis by hydroxide ion (pH > 11) that is typically used in the formose reaction (Mizuno and Weiss 1974;Harsch et al 1983Harsch et al , 1984. Moreover, catalysis by inorganic surfaces allows products formed on one surface to diffuse to a second surface for either stabilization or further catalytic transformation.…”